The RF system for the CEBAF polarized photo injector
Jefferson Lab's CEBAF electron accelerator has recently begun delivering spin-polarized electrons for nuclear experiments. Spin-polarized electrons are emitted from a GaAs photocathode that is illuminated with pulsed laser light from a diode laser synchronized to the 3rd subharmonic (499 MHz) of the accelerating cavity frequency (1497 MHz). Up to three experimental halls (A, B, and C) are served by the photoinjector each with their own beam requirements. To accomplish this, three independent diode lasers are synchronized and combined to illuminate the GaAs photocathode emitting a 1497 MHz pulse train of electrons. In addition, an RF bunching cavity, approximately 2m downstream from the photocathode is used to compensate for space charge effects at the higher beam currents. The RF system that controls these elements is a modified VME based system. Custom RF VME modules control phase and amplitude for each laser diode and the bunching cavity. Power requirements were satisfied with commercial RF amplifiers, 5 W for the diode lasers and 10 W for the bunching cavity. Simple software algorithms using the EPICS control system correct phase and amplitude drifts. The RF system is compact, simple and allows for easy hardware or software modifications.
- Research Organization:
- Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 755345
- Report Number(s):
- DOE/ER/40150-1443; JLAB-ACT-98-06
- Country of Publication:
- United States
- Language:
- English
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